This invention generally relates to motor driven surgical systems, and, more particularly, to a system for controlling the relative positions of components of an all digital motor controlled surgical system.
Digital speed control systems for controlling the rotational speed of brushless motors used, for example, with arthroscopic cutting devices are now well known.
These brushless motor controlled devices typically adapt to a surgical assembly and use an all digital well defined system such as that disclosed in U.S. Ser. No. 135,297 and U.S. Pat. No. 5,270,622, referred to above. They provide excellent control over the rotational speed and position of the motor armature, which enables precise and accurate control of the surgical assembly through an appropriate gear reduction between motor and assembly. Such digital control systems provide an advancement over the prior analog controlled systems using, typically, brushless motors.
In all of these motors, however, the relative position of the rotatable driven surgical member to the fixed housing in which it rotates, and in particular, the relative opening of, for example, a cutting aperture at the distal tip of the surgical device is unknown. In this respect, both brushless (all digital) and brush motors suffer the same difficulty, in that the nature of the aperture is unknown to the control system and, in particular, there was no way of maintaining any fixed relationship, known to the control system, between the rotatable portion of the removable rotary tip of the surgical device and its enclosing fixed housing.
It is therefore an object of the invention to improve the control over the relative location of the rotational portion of the driven surgical member, and in particular, to provide an apparatus which enables the physician to improve the efficiency and effectiveness of an arthroscopic cutting device and the accuracy with which the cutting process proceeds.
It is a general object of this invention to advance the state of the art in the control of brushless motors, particularly in connection with controlled arthroscopic cutting devices.
Another object of this invention is to provide an all digital motor controlled surgical cutting device having improved cutting effectiveness, accuracy, and response repeatability.
Another object of the invention is to provide an improved motor controlled system which has particular application in surgical procedures.
Yet another object of the invention is a method and apparatus which accurately and repeatably control motor driven surgical tools.